Endogenous antigens can be cross-presented to MHC-II molecules by certain dendritic cells through a cellular process called autophagy.
1. Cellular cytoplasm containing endogenous antigens is engulfed and placed in a autophagosome.
2. After a lysosome fuses with the autophagosome, these endogenous proteins are degraded by lysosomal proteases into peptides.
3. The peptides are directly transfered from the autophagolysosome to the vesicles containing the MHC-II molecules.
4. The MHC-II molecules with bound peptides are then transported to the surface of the dendritic cell where they can be presented to naive T4-lymphocytes.